Thickness effects of fracture characteristics of coal seam and surrounding rocks in fully mechanized top-coal caving face

The influence law of caving thickness of fracture characteristics of coal seam and surrounding rocks in fully mechanized top-coal caving face were researched by numerical simulation,combined with laboratory experiment and in-situ measurement. The results show that the fracture range of coal seam and top-coal and caving thickness have non-linear direct proportion relations,that is,the fracture range of coal seam and top-coal increase with the increase of caving thickness; the most serious fracture range of coal seam are situated in front caving face,the fracture range of topcoal is bigger than the coal seam of face,the fracture range of the tailentry is bigger than the headentry,and narrow and small coal pillars are damaged with close to the caving face,so the emphasis of entry surrounding rock support in fully mechanized top-coal caving face is gate beside gob from deformation control point of view.